The closing of U.S. embassies in 21 predominantly Muslim countries and a broad caution about travel during August that the State Department issued on Friday touched off debate Sunday over the National Security Agency’s sweeping data collection programs.

Congressional supporters of the program, appearing on Sunday morning talk shows, said the latest rounds of warnings of unspecified threats showed that the programs were necessary, while detractors said there was no evidence linking the programs, particularly the massive collection of cell phone records of hundreds of millions of Americans, to the vague warnings of a possible terrorist attack.

Meanwhile, there were no reports of violence or unusual activity in any of the countries where the United States had kept its embassies and consulates closed when they would have ordinarily been open on Sunday. Nevertheless, the State Department announced that embassies and consulates in 16 countries would remain closed throughout the week, including four African nations that had not been on the original list. Diplomatic posts in five other countries would reopen Monday, the State Department said, including those in Afghanistan and Iraq, where terrorist attacks have been frequent.